correct static string clearing loop (closes #16906)
merge 3.3 (#16906)
Issue #16876: Optimize epoll.poll() by keeping a per-instance epoll events
buffer instead of allocating a new one at each poll().
#16852: test_genericpath, test_posixpath, test_ntpath, and test_macpath now work with unittest test discovery.  Patch by Zachary Ware.
#16852: merge with 3.3.
Use correct methods in unittest.mock examples.
Merge unittest.mock examples fixes.
#16897: test_bisect now works with unittest test discovery.  Initial patch by Zachary Ware.
#16897: merge with 3.3.
#16896: test_asyncore now works with unittest test discovery.  Patch by Zachary Ware.
#16896: merge with 3.3.
#16888: test_array now works with unittest test discovery.  Patch by Zachary Ware.
#16888: merge with 3.3.
#16898: test_bufio now works with unittest test discovery.  Patch by Zachary Ware.
#16898: merge with 3.3.
#16905: test_bufio now works with unittest test discovery.  Initial patch by Berker Peksag.
#16905: merge with 3.3.
#16910: test_bytes, test_unicode, and test_userstring now work with unittest test discovery.  Patch by Zachary Ware.
#16910: merge with 3.3.
Issue #16076: make _elementtree.Element pickle-able in a way that is compatible
with the Python version of the class.

Patch by Daniel Shahaf.